The present application relates to touchless faucets, and more particularly to such faucets that employ a light beam to sense presence of a person and activate the faucet in response to that sensing.
In hospitals, public rest rooms, and other facilities, it is commonplace to provide a faucet which is turned on and off without requiring the user to touch the faucet. The prior art is replete with devices for sensing the presence of a user and, in response thereto, activating a solenoid valve assembly that controls the flow of water to a faucet. A common sensing technique, as described in U.S. Pat. No. 4,915,347, involves transmitting an infrared light beam into a flow region underneath the outlet of the faucet spout, where a user's hands or other objects are placed for washing. A hand or object so placed reflects some of the infrared light beam back toward the faucet, where that reflected light is detected by a sensor mounted either on or adjacent the faucet. Detection of reflected light at the sensor indicates the presence of a user in front of the faucet. In response to receiving the reflected light, the sensor emits an electrical signal that causes the solenoid valve to open, sending water from the faucet. When the detection of reflected light ceases, the solenoid valve is de-energized, terminating the flow of water.
A problem with such proximity activated faucets is that room elements near the faucet, such as a mirror or shiny sink surfaces, can reflect light back to the sensor, thereby falsely triggering the flow of water. Inanimate objects, such as handbags, placed on the front edge of the sink also can falsely cause faucet operation. The false activation of the faucet not only wastes water, but may result in water overflowing the sink, if an unattended object also is blocking the drain opening.
Prior touchless faucets were not practical for kitchen sinks which are used for operations, such as draining water from a cooking pot or cutting vegetables, during which water from the faucet is not desired. Thus during such activities, the presence of a hand or other object beneath the faucet outlet should not activate the flow of water.